Loud speaker



June 5, 1928. 1,672,493

R. T. KINGSFORD LOUD SPEAKER 2 Sheets-Sheet Filed Nov. 1925 I 6 6 v I w d. V

BY (M (9M ATTORNEY."

June 5, 192s. 1,672,493 R. T. KINGSFORD LOUD SPEAKER Filed Nov. 5, 1925 2 Sheets-Sheet 2 1 1 ATTORNEY:

Patented June 5, 1928.

' UNITED sTAT s PATENT... OFFICE.

RUSSELL 'I'. KINGSIOBD, OF WYNCOTE, PENNSYLVANIA, ASSIGNOB TO ATWATER '1! MANUFACTURING COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPQBA- TION OF PENNSYLVANIA.

, LOUD airman.

- Application filed November 8, 1923. Serial No. 872,512.

- My invention relates to telephone structure for converting sound-representing current into soundwaves, or vice versa, and more particularly, for utilization in connec. tion with horns and like amplifiers utilizable for any purpose, and articularly as socalled loud speakers. 1n connectlon with radio telephonic apparatus.

My invention resides in featureaof structure, combination and arrangement of parts of the character hereinafter described.

For an illustration ofsome of the Various forms my invention make take, reference is tohbehhad to the accompanying drawings, in w 1c Fig. 1 is a vertical sectional view of ap-" Fig. 7 is a perspective view of a terminal bracket.

Fig. 8 is a side elevational view, partly in vertical section, of a horn structure and base.

Fig. 9 is a vertical sectional view, partly in side elevation, of a form of my apparatus utilizable in connection with the sound arm of a phonograph.

Fig. 10 is a side elevational view'of my apparatus inoperative relation with the horn structure of a phonograph.

Referringto the drawings, 1 is the hollow base, as of metal, having the chamber or cavity 2 and the neck 3 provided with the passage 4 extending from the chamber 2 to the upper'end 5 of the neck 3.- The neck 3 .is' pre erably of reduced diameter, as indicated at 6, extending-to the upper end of the neck 3 from the shoulder 7, upon which rests the lower end 8 of the horn 9, which is rotatable about a vertical axis upon the suitably shoulder 7, the horn passage registering .and communlcatmg with the passa e 4.

Attached to the lower end 0 the base 1 is the sheet of felt,-;cloth or equivalent material 10. t Y

Disposed within the-chamber 2 in the base 1 is the supportor casing 11, of any suitable material, as metal, such as brass, die cast .alloy or the like. The casing 11 has the lugs the casing 1. In the example illustrated, the annular flange 15 of the cap 14 is exteriorly threaded andthreads into the casing member 11, whereby upon rotation of the cap 14 with respect to the casing 11 the cap approaches or recedes from the upper end .of the casing 11. Extending outwardly from the flange 15 is the integral annular flange or shoulder lhavin upon its periphery the serrations 14 -form1n'g a suitably rough-- ened grip for the hand for rotatably adjusting the cap 14 with respect to the casing 11. Adjacent 1ts center the cap 14 has the recess or depression 16, on opposite sLdes of which are dlsposed the raised portions or bosses 17 extending somewhat above the portion or depression 18 joining the recess 16. Screw threaded studs 19 have knurled-or roughened heads 20 molded in the bosses 17.

sis

adjustably supported or secured to which are threaded the nuts 21 to hold the magnet M fixedly in position against the iron or steel ole pieces 22 held fixedly in position by t e studs 19 and nuts 21 between the magnet M and the bosses 17. Integral with the pole pieces 22 are the upstanding poles 23, Integral with the cap flange l5 arethe bosses or abutmentsi24, having faces-with which engage the circular or curved faces 25 of the pole pieces 22 for accurately and fixedly locating the pole pieces 22 and poles 23. I

Upon each of the poles 23 is disposed a i. spool or coil support 26, suitably held in supports 26 are the ma net windings, connected in series with eac other, the magnet win'dlng having the terminals 28, 28, preferably in the form of sheet conducting material, each connected to an upstanding terminal bracket 29 having the horizontal arm 30 and the downwardly extending lug 31, struck up from the member 30, and extending into a recess 32 in the cap 14. The threaded studs 33 have the heads 34 molded in the cap 14. Each member 30 has a hole 35 through which a stud 33 extends. Threaded upon each stud 33 is a nut 36, by which the member 130 .and bracket 29 are fixedly secured in place on the inside of the cap '14, the lug 31 preventing rotation of and holding the bracket 29 in predetermined fix'ed position. Between the second nut 37', threaded upon the stud 33, and the nut 36 is held the terminal 38 upon the flexible conducting cord 39, the two cords being formed into a cable 40 extending through a hole in the central boss 14 on the cap 14, and thence through the insulating bushing 41 threaded into the base 1. The cords 39 at their remote ends are provided with the usual cord tips 42 or other suitable means for connecting the magnet winding in any suitable circuit, as, for example, in the anode circuit of a detector or audio frequency amplifying tube of the audion type, as commonly employed in radio telephone receiving apparatus. 1

From the foregoing description it is apparent that the magnet system of the telephone is fixedly, supported upon a cap or casing closure member forming therewith a unit adjustable longitudinally of the axis ot the casin member 11.

At the lower end of th sound passage 4-, inthe. neck 3 the base 1 is preferably recessed or chambered, as indicated at 43.

- faces.

The magnet poles 23 are preferably symmetrically. disposed with respect to the coincident axes of the'cap 14, casing 11 and sound'passage 4, and extending across and above the poles 23 is the circular diaphragm D, of magnetizable material, as soft iron, which may be plated on either or both sur- Preferably, the diaphragm D is slightly cupped or concaved upwardly, as

/ indicated in Fig. .1, whereby the diaphragm is"in effect bowed ,or arched downwardly with. its center portion approaching the ends of the magnetv poles 23.- :The outer edge of the diaphragm is confined between the soft rubber washers-'44 and 45, the former -disposed; within the casing .11 and lying Y, "gai-nst; 1'1, and I the latter lying between the diaphragm and the preferably rigid rin 46, of iron or other suitable ma terial, and supported by the resilient member or annular spring 47, preferably waved or circumferentially undulated, as indicated. 7n The spring 47 is in turn supported by the inner end of the flange 15 of the cup 14, whereby, upon rotation of the cap 14, it advances into or withdraws from the casing 11, thereby varying. the compression 7 upon the spring 47 and thereby varying the compression exerted by the ring 46 upon the washer 45, diaphragm D and washer 44.

lhe adjustment of the cap 14 accordingly effects a variation of the distance between the ends of the magnet poles 23 and the diaphragm D, and simultaneously varies the confining torce exerted upon the outer edge of the diaphragm D. By employment of either one of 'or both of the easily compressible washers 44.and-45, as the cap 14 and the magnet system are adjusted toward the diaphragm D, the ring 46 evenly distributes the pressure exerted by spring 47 and the diaphragm D recedes slightly from the ends of the poles 23, due to compression of one i or both of the washers 44 and 45, but the movement of the poles 23 toward the dia- 'phragm is greater than the recession of the diaphragm D from the poles, whereby by the adjustment described the magnet poles approach nearer the diaphragm, and by the same adjustment the diaphragm is more firmly held at its periphery or outer edge.

Adjustment of the poles 23 with respect 9 to the diaphra m D is desirable, particularly in radio telep one receiving apparatus, because of the wide range within which theamplitude of the sound-representing current varies. With sound-representing current of large amplitude traversing the magnet winch ing, the poles 23 are preferably at a greater distance from the diaphragm D than in the case when the amplitude of the sound-representing current is small. Ordinarily, a suitable adjustment is effected by rotating the cap 14 to cause the. poles 23 to app-roach the diaphragm D so closely that the latter will be attracted or snap into contact with the poles 23, whereupon the cap 14 is rotated in opposite direction to withdraw the poles. 23 slightly to such position that the diaphragm D is just slightly separated from the ends of the poles 23;

While the apparatus above described in connection with Figs. 1 to 8 inclusive has related more particularly to a loud speaker or amplifier horn unit, similar apparatus maybe utilizedfor applicationto the sound armandhorn of a phonograph, as indicated in Figs. 9 and; 10. As indicated in Fig. 9, the casing 11 is provided with-the end wall or closure member teamma e or -integral with the casing 11. and" provided w-ith the short neck 3 having-the sound-lpassage e As indicated, the neck 3 is adapted to slip into or connect to the end of'the tube or sound arm 49 of aphonograph sound arm or horn system comprising the tube '49 pivotally -attched to the hollow chamber 50 communicating with the sound arm or tubular member 51, whose sound passage communicates with the phonograph horn 52.

By the arrangement shown, the casing 11, with its cap 14 and the magnet, diaphragm and other described parts,. is attached as a unit to the sound armor tubular member 49 in place of the usual soundreproducing structure, of a phonograph;

In the structures of the character hereinbefore'described, the pressure exerted by the spring 47 upon the ring 46 reacts upon the end of the cap flange 15, thereby pressing its threads against the threads on the casing 11, thereby firmly holdingthe'magnet system with nicety and exactitude in the position to which adjusted by rotation of the cap 14. Furthermore, with the magnet system adjusted to predetermined position by adjustment of cap 14 the spring 47 will follow the ring 46 and firmly hold the diaphragm D between the rubber rings 44 and ,45 notwithstanding their loss of resiliency or flattening as they deteriorate with age.

The diaphragm D, particularly when of soft or'Swedish iron, mild steel or other oxidlzable'r or corrodible material, *is preferably electro-plated on either or both sides, first with copper and then with zinc, to

effect a finish or surface avoiding the need for lacquer, varnish or the like commonly employed to prevent rust vor corrosion. Furthermore, the application of paint, la c quer, varnish or the like to a diaphragm to some extent affects its sound-reproducing characteristics, and it is accordingly preferred to use a diaphragm free of paint, varnish, lacquer or the like. The electroplate is preferably sand-blasted on either or both sides of the .diaphragm to remove scale and impart suitable character to the surface.

It is preferred that the convex sideof the diaphragm D be presented to the magnet system, as illustrated. and above described, because the sound waves reproduced by the diaphragm correspond to greater degree and with greater faithfulness with the sound- .representing current traversing the magnet winding, and because the volume of the reproduced sounds is greater, than is the case when-the concave side of the diaphragm is presented to theniagnet system.

It will be understood that while the concavity of the diaphragm is curvilinear,- it may be of other outline, as conical, frustoconical or the like, or the diaphragm may be in the .form of a-many-sided pyramidof f slight altitude, and having, if desired, a

small flat center portion. Where the con cavity is of-curvilinear outline, it may comprise a surface of revolution whose generatrix is an arc of either a circle, an ellipse, or any other suitable flat curve.

In radio telephonic reception the soundrepresenting current, as appearing/in the anode circuit of the detector audion or vacuum tube, or in the anode circuit of an audio frequency amplifier tube, varies in magnitude through a relatively great range and has an average value which is quite high when receving from any. given transmitting station; and when receiving from diflerent transmitting stations, the magnitudes of thesound-representing currents as caused by such transmitting stations are relatively widely different. The concavity of the diaphragm is of advantage under these widely varying conditions of strengths of sound-representing currents, because to produce a given deflection'of the diaphragm toward the magnet poles a greater force must be applied thereto b. the magnet system than in case the diap' ragmis straight or fiat. This characteristic does not, however, reduce the total a litude of the diaphragms vibration, but/1n fact increases it, since the force requir d to deflect the diaphragm in opposite direction or away from the magnet system/ is less than would be the case with a flat diaphragm. Furthermore, because of the aforsaid increased resistance to deflection in one direction and reduced resistance in the other directionv offered by the concave diaphragm, the timbre or quality of a voiceor music-representing current is the' more faithfully reproduced, since the higher harmonic components of the sound-representing current, upon which depend the timbre or quality, are able adequately to affect the diaphragm which, because of its resistance to deflection,

may approach the magnet poles the closer,

as in the first case to be faithfuLor. without great or substantial dist lOIl. The extent of deflection of the c cave diaphragm under the influence of the magnet system more closely approximates proportionality to change in length of air gap, or distance between diaphragm and magnet poles, than in the case of'the ordinary or straight dia- All phragm. With the concave diaphragm, different degrees of deflection thereof correspond more closely or are more nearly proportional to the different degrees in amplitude of the sound-representing current traversing the magnet winding, and therefore the reproduced sound corresponds more closely, as regards lack of distortion, with the sound-representing current.

By way of example merely, it may be stated that when the diaphragm is about two and one-half inches in dian1eter,'and has a thickness of about .012 inch, the extent of concavity is about .015 inch, the diaphragmas such having this concave or cupped conformation before placement in the field of the magnet system, which exerts a pull thereon whose magnitude is varied by the sound-representing current. When the diaphragm is stationary in the magnetic field, as when no fluctuating or sound-representing current is traversing the magnet winding, the air gap between diaphragm and the magnet poles may preferably be of the order of .01 inch, with the magnet poles exerting a pull of seven pounds on the diaphragm, when the cap has been rotated insuch direction as to withdraw the magnet system from contact with the diaphragm, as hereinbefore adverted to. A normal pull of upwards of three of four pounds, and preferably of the order of seven pounds, upon the diaphragm with zero current in the magnet winding has been found by me to be of advantage, and this is made possible by recourse to a concave diaphragm which may approach the magnet poles as closely as a flat diaphragm on which may be exerted by the poles only a considerably smaller normal pull.

What I claim is: I

1. In apparatus of the character described, the combination with a diaphragm-supporting member, of an annular member of resilient material disposed upon said supporting member, a diaphragm disposed upon said annular member, a member adjustable with respect to said supporting member, and a bowed annularspring disposed between said last named member and said diaphragm.

2. In apparatus of the character described,

the combination with a diaphragm-supporting member, of a diaphragm, an annular member of resilient material engaging said diaphragm, a member adjustable on said supporting member, and a bowed annular spring intervening between said last named member and ,said 'annular member of resilient material for communicating pressure to said diaphragm through said annular member of resilient material.

3. In apparatus of the character described, the combination with a diaphragm supporting member, of a diaphragm, an annular Amember of resilient material engaging said diaphragm, a substantially rigid annular member engaging said annular member of resilient material, a member adjustable on said supporting member, and a bowed annular spring confined between said last-named member: and said second named annular member.

4s Inapparatus of the character described, the combination with a diaphragm-supporting member, of a pair of annular members of resilient material one of which is disposed upon said supporting member, a diaphragm disposed between said annular members, a member adjustable upon said supportin member, and an annular spring confine between said last named member and one of said first named annular members.

5. In apparatus of the character described, the combination with a diaphragm-supporting member, of a pair of annular members of resilient material one of which is disposed upon said supporting member, a diaphragm disposed between said annular members, a substantially rigid annular member disposed upon one of said first named annular members, a member adjustable upon said supporting member, and an annular spring confined between said last named member and said substantially rigid annular member.

6. In apparatus of the character described, the combination with a support, of a diaphragm, resilient means confined between said diaphragm and said support, a magnet system co-aoting with said diaphragm, a member carrying said magnet system and adjustable on said support, and an annular spring disposed between said last named member and said diaphragm.

7. In apparatus of the character de-v scribed, a casing, a diaphragm therein, an

annular member of resilient material confined between said casing and said diaphragm, a-c'ap having a flange extending into said casing and having threaded engagement therewith, and an undulated annular spring confined between the 'end of said flange and said diaphragm.

8. In apparatus of the character described, a casing, a diaphragm therein, an annular member of resilient material confined between said casingl. and said diaphragm, a second annular member ofresilient material on the opposite side of said diaphragm, a cap having a flange extending into said casing.

and having threaded engagement therewith, and an undulated annular spring, confined between the end of said flange and said second annular member of resilient material.

9. In apparatus of the character described, a casing, a diaphragm therein, an annular member of resilient material confined between said casing and said diaphragm, a second annular member of resilient material on the opposite side of said diaphragm, a

ing threaded engagement therewith, and an" undulatedannular spring confined between the end of said flange and said substantially ri id annular member.

O. In apparatus of the character described the combination with a casing, of

a diaphragm therein, resilient supporting means, for said diaphragm, a magnet system co-acting with said "diaphragm, a cap carrying said magnet system, said cap having a flange extending into said casing and having threaded engagement therewith, and an annular spring confined by the end of said flange and exerting pressure on said resilient supporting means.

11. In apparatus of the character described, the combination with "a metallic casing, of a resilient ring on said casing, a diaphragm supported thereby, a magnet system, a cap of molded insulating material carrying said magnet system and rotatably adjustable upon said casing for effecting adjustment of said magnet system with respect to said diaphragm, and an undulated annular spring confined between said cap and said diaphragm. I

12. In apparatus of the character described, a metallic casing, a diaphragm supported thereby, a magnet system co-acting with said diaphragm, a cap of molded insulating material, a member molded in said cap, and means detachably sec said magnet system to said member, sa d cap threaded upon said casing to effect by rotation of the cap adjustment of said magnet system with respect to said diaphragm.

13. In apparatus of the, character described, a metallic casing, a diaphragmsupported thereby, a magnet system co-acti'ng with said diaphragm, a cap of molded insulating material carrying said magnet system and threaded upon said casing to effect by rotation of the cap adjustment of said magnet system with respect to said diaphragm, and an annular spring engaged by said cap and exerting upon said diaphragm a pressure dependent upon the position of said cap with respect to said casing,

14. In apparatus of the character described, aocap of molded insulating material, a magnet system carried by said cap and comprising a magnet, and a member molded in said cap for detachably securing said magnet system to said cap.

15. In apparatus of the character described, a cap of molded insulating material, a magnet system. carried thereby comprising tmagnet, a member molded in said cap, and means engaging said member and said magnetior detachably holding said magnet system to said cap.

. 16. In apparatus of the character described, t-he' combination with a cap of molded insulating material, of a magnet system carried thereby comprising a magnet,

a stud molded inisaid cap' and extending through said magnet,-and means engaging said stud for detachably holding said magnet to said cap.

17. In apparatus of the character described, the combination with a cap of molded insulating material, of a magnet system comprising a magnet and pole piece structure, and a member molded iusaid cap and detachably securing said magnet .and pole piece structure to each other and to said cap.

18. In apparatus of vthe character d scribed, the combination with a cap of molded insulating material, of a detachable magnet system carried by said cap and comprising a. magnet and pole piece structure having registering apertures, said pole piece structure disposed between said magnet and a wall of said cap, and means molded in said scribed, the combination with a cap of molded insulating material, of a detachable magnet system carried by said cap and comprising a pole piece,-means for securing said pole piece to said cap, and a boss integral with said cap adjacent which said pole is disposed. I 1

j 20. In apparatus of the character de scribed, the combination with a cap of mold- .ed insulating material, of a magnet system com ri a le'piece havin an aperture, mea s through said aperture for holding said pole piece to said cap, and a boss integral with said cap disposed adjacent said pole piece.w

21. In apparatus of. the character described, the combination with a cap of molded insulating material, of a magnet winding carried by said cap, and means for effecting connection with said winding comprising a terminal bracket having an arm lying against a wall-0f said cap and an upstandin member, means for securing said arm to sai cap, and a connection from said upstanding member .to said winding.

22. In apparatus of the character described, the combination with a cap of molded insulating material, of a magnet winding carried by said cap, and means for effecting connection with said windingcomprising a terminal bracket, means for securing said bracket to said cap, a connection from said bracket to said winding, said cap having'a recess adjacent said bracket, and :1 lug on said: bracket extending into said recess.

23. In apparatus of the character described, the combination with'a cap ofimolded insulating material, of a magnet winding carried by said cap, and means for eflecting connection with said winding comprising a terminal bracket, a stud molded in said cap and extending through a perforation in said bracket, a connection from said bracket to said winding, said cap having a recess adjacent said stud, and a lug on said bracket extending into said recess. 24. In apparatus of the character described, a casing, a diaphragm therein, a cap having a flange extending into said casing and having threaded engagement therewith, an annular member of resilient material disposed between said diaphragm and said flange, and an undulated annular spring engaged by said flange and transmitting pressure to said diaphragm through said annular member of resilient material.

25. In apparatus of the character described, the combination with a concave-convex diaphragm, of a magnet system comprising a permanent magnet system spaced by air gap from and disposed on the convex side thereof and normally exerting a pull there" .on of magnitude upwards of three pounds.

26. In apparatus of the character described, the combination with a concave-convex diaphragm, of a magnet system comprising a permanent magnet system spaced by air gap from and disposed on the convex side thereof and normally exerting a pull thereon of magnitude of the order of seven pounds.

27. A telephone diaphragm which of itself is normally concavo-convex to an extent of the order of the thickness of the diaphragm.

28. A telephone diaphragm of substantially uniform thickness and which of itself is normally concavo-convex to an extent of the order of thickness of the diaphragm.

29. Telephonic apparatus comprising a diaphragm which is of itself concavo-convex to an extent of the order of magnitude of the thickness of said diaphragm, and a magnet system comprising a permanent magnet and a winding there or disposed upon one side of said diaphragm.

30. Telephonic apparatus comprising a diaphragm which is of itself concavo-convex to an extent of the order of magnitude of the thickness of said diaphragm, and a magnet system comprising a permanent magnet and a winding therefor disposed on the convex side of said diaphragm.-

31. Telephonic apparatus comprising a diaphragm which of itself is concavo-convexto an extent of the order of its thickness, resilient means supporting said diaphragm adjacent its periphery, and a magnet system disposed on one side of said diaphragm.

32. In apparatus of the character described, the combination with a diaphragm, of members on opposite sides thereof and confining said diaphragm substantially aevaeee throughout its entire circumference on both sides thereof, a member adjustable toward and away from said diaphragm, and a bowed annular spring disposed between said dia-. phragm and said adjustable member.

33. In apparatus of the character described, the combination with a diaphragmsupporting member, of an annular member of resilient material disposed upon said supporting member, a diaphragm disposed upon said annular member, a second. member of resilient material on the opposite side of K said diaphragm and engaging the same substantially throughout its entire circumference, a member adjustable with respect to said supporting member, and a bowed an nular spring disposed between said last named member and said diaphragm.

34:. In apparatus of the character dc scribed, the combination with a diaphragm supporting member, of an annular rnember, of resilientmaterial disposed upon said supporting member, a diaphragm disposed upon said annular member, a second member of resilient material on the opposite side of said diaphragm and engaging the same substantially throughout its entire circumference, a substantially rigid annular member engaging said second member of resilient material, a member adjustable withrespect to said supporting member, and a bowed annular spring disposed between said substantially rigid annular member andsaid member adjustable with respect to said supporting member.

35. In apparatus of the. character described, a metallic casing, a diaphragm supported therein, a magnet system, a cap of moulded'insulating material carrying said magnet system, an exteriorly threaded flange on said cap engaging in said casing, and an integral annular ange on said cap extending radially outwardly across the end of said casing for eflecting a manual rip for rotatable adjustment of said cap wit respect to said casing.

36. Telephonic a paratus comprising a diaphragm which 0 itself is concavo-convex to an extent of the order of its thickness, resilient means supporting said diaphragm adjacent its periphery on one side of said diaphragm, and a magnet system disposed onsaid side .of said diaphragm.

37. In apparatus of the character described, the combination with two diaphragm-confining members, of a diaphragm disposed between them, a member of resilient material disposed between said diaphragm and one of said members, and a bowed spring member disposed between said one of said members and said member of resilient material.

38. In apparatus of the character described, the combination with two diaphragm-confining members, of a diaphra m disposed between them, resilient material isposed on opposite sides of said diaphragm scribed, the combination with two dia-' phragm-confining members, of a diaphragm disposed between them, a member of resilient material disposed between said diaphragm and one of. said members, a bowed spring member disposed between said one of saidmembers and said member of resilient material, a magnet system on one side of said diaphragm, and means for adjusting said magnet system with respect to said diaphragm.

40. In telephonic apparatus of the character described, the combination with two diaphragm-confining members, of a diaphragm disposed between said members, re-

silient material disposed between the periphery of said diaphragm and one of said members, and a plurality of spring contacts disposed between the other of said members and said diaphragm for transmitting pressure to the periphery thereof at a series of circumferentially spaced regions.

41. In telephonic apparatus of the character described, the combination with two diaphragm-confining members, of a diaphragm disposed between said members, resilient material disposed between the periphery of said diaphragm and one of said members, and an undulatory annular spring disposed between the other of said members and said diaphragm for transmitting pressure to the periphery thereof at a series of circumferentially spaced regions.

In testimony whereof I have hereunto aflixed my signature this 1st day of N ovember, 1923.

RUSSELL T. KINGSFORD. 

